Double-filament vacuum tube



C. MURRAY DOUBLE FILAMENT VACUUM TUBE March 24, 1925.

Filed Aug. 7, 1923 6 4 w gmmm ado-(neg Patented 24, 1 925.

ToaZZw-homit uum tubes and more UNITED STATES- CHARLES MURRAY, OF WABHINGTON, DIEDBIO'T OF COLUMBIA.

noUnrn-rmnmir vacuum TUB-E.

Be it known that I, CHARLES MURRAY,

a citizen of the United States, residing at Washington, District of Columbia, have invented certain new and useful Improvements in Double- Filament Vacuum Tubes, of wh-ichthe following is a specification.

This invention relates in general to vacarticularly to an improvement in double lament vacuum tubes" over the type disclosed in my pendin plication, Serial No. 632,128 filed April 14, 1923. 1

It is proposed toconstruct a vacuum tube having an outer glass container and a cylindrical plate, two filaments with a grid equidistant therebetween, being arranged in the circular plate. The object of so placing the filaments on opposite sides of the grid e ectrode is to allow sufiicient space between the filaments to prevent the filament not in use from becoming heated from absorption from the one being used.

Another object is that by suchnrrangement the same relative distance is accurately maintained between elements during the operation of either filament, and since the cold filament is always at zero potential, it is assumed the tube will operate as if no extra filament were contained in it, and no appreciable difference in working characteristics will be noticeable by changing the filaments.

Referring more particularly to the draW- ing, a glass tube 1 is provided with an up er and lower base, 4 and 5 respectively. n-\

teriorly the tube 1 is a cylindrical plate. A-

grid electrode, 13, and two filaments, 2 and 3, are placed within a cylindrical plate, 14, and are arran ed equidistant from each other and the p ate 14. The plate 14, grid 13, and filament '2, are-provided with leads 14, 13, and 2, respectively, arranged with kee rs, 6, and knife blade contacts 7, the

lea passing through the lower insulated Application med A e-1, 1923. Serial No. 056,218;

base 5, The leads 3' from the filament, 3 pass through the upper insulated base and are provided with keepers 12, and knifeblade contacts 11. A suitable switch, 8, is arranged betweentheleads 3' and the'l'eads 9 to the filament source of energy. 'By arranging the filaments and grid in this manner the tube may be operated by shifting alternately from one filament to the other, allowing each in its turn to, burn the same number of hours. In this wayy'the maximum efliciency and longevity of the filaments is assured.

The action which takes place within a vacuum tubeduring its operation is due to the electron flow which causes a1 wasting away of the filament, and the life of the tube depends entirely upon the length of time required to exhaust the filament. By adding an extra filament, which may be done by merel throwing a switch, the life of the tube is engthened over the life of a tube with one filament; The cost of such redesigning of the conventional tubes would be practically no more than the actual cost of the additional filament.

The additional feature of placing the 1d between the two filaments and spacing tfi em atequal distance from the grid, and the circular plate enclosing them, makes it possible to keep the inactive filament from becoming overheated from the active filament, and

tend to keep the operation of the tube constant, and alike in working characteristics when either filament is brought into operation.

Claims:

1. In a radio oscillating tube, a cylindrical plate, a centrally disposed gridelectrode, a plurality of independent energizing filaments, arranged on diametrically oppoe site sides of 'said grid electrode, and means for connecting said grid, plate, and filaments to external conductors.

2. In a radio oscillating tube, a cylindrical plate, a centrally disposed, grid'elec trode, aplurality of independent energizing filaments arranged on d ametrically opposite sides of and equidistant from said id, and means for connecting said grid, p ate, and filaments to external conductors.

3. In a radio oscillating tube, a cylindrical plate, a plurality of independent energizing filaments arranged interiorly of said plate, a grid located centrally between said filaments, the distances between the v g a. 1,oao,ea7n

'd and each filament and between each of which is provided with knife blade con- 1'0 fil ament and the plate being equal, and tacts and keepers, said plate, grid and one means for connecting said grid, plate, and 'of saidfilaments being connected to suitfilaments to exteinal conductors. -able external conductors through said lower 4. In a radio oscillating tube, a cylmbase, the other of said filaments being condrical plate, a plurality of independent nected to suitable external conductors 15 energizing filaments arranged ,mtemorly of through said upper base, said late, a grid located centrally between In testimony whereof I affix-m si ature. said 1aments,'an upper and lower baseeaeh CHARLES-M AY. 

